Exhaust gas turbocharger with auxetic structures

ABSTRACT

An auxetic material or auxetic structures in an exhaust gas turbocharger having a shaft and at least one compressor wheel arranged on the shaft, a turbine wheel and a housing in which the shaft, the compressor wheel, and the turbine wheel are arranged. At least one part of the housing includes an auxetic material with a negative Poisson&#39;s ratio.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The invention relates to an exhaust gas turbocharger.

2. Description of the Related Art

Conventional exhaust gas turbochargers are employed for increasing powerand optimising combustion. For a good and complete combustion in theengine, a certain mixture ratio is necessary (stoichiometric fuelratio). During the charging of the exhaust gas turbocharger, the densityof the intake air is increased and the air quantity thus enlarged.Through the supercharging, the degree of filling and thus the efficiencyof the internal combustion engine is significantly improved.

The heart of the turbocharger is the running gear consisting of turbinewheel with shaft and compressor wheel, which are arranged in aturbocharger housing. The turbine wheel is located on the exhaust gasside and is mostly permanently connected to the shaft. The compressorwheel is mounted on an opposite end of the rotor shaft. Depending onembodiment, the wheels are typically equipped with rotor blades and forma gap towards the housing on the end side. The gap width has a directinfluence on the efficiency of the turbocharger. Depending on therotational speed of the shaft, different elongation proportions alsooccur on the various rotating and non-rotating components—these therebyresult in variable relative positions.

Thus, the gap between the blade tips and the housing wall changes aswell. Regarding the elongation behaviour, attention is paid inparticular to the so-called transient elongation behaviour between rotorand housing while passing through a cycle. This respective transientelongation behaviour of rotating and non-rotating components differssignificantly. There is consequently a high risk for a gap bridging whenthe blade wheel tips rub against the housing. Such a risk of an instanceof rubbing between housing and blade tip is present in particular duringthe running-up of the exhaust gas turbocharger.

In order to avoid dangerous and/or impermissible operating states in thetransient operation between components that are moveable relative to oneanother, the nominal gaps are consequently dimensioned adequately largein the prior art. By way of this, a rubbing or bridging of the gap withcontact on the housing during the transient operation can be avoided,but a gap that has been dimensioned correspondingly large leads to areduced efficiency during the subsequent steady-state operation of theexhaust gas turbocharger.

In the event of bursting—during the failure of rotatingcomponents—dangerous situations with fragments of the exhaust gasturbocharger being flung about can develop. In the prior art, differentburst protection devices are proposed for this purpose.

To prevent component fragments exiting in defined failure scenarios ofrotating components, for example, solid wall thicknesses are provided inconventional housing structures and/or complex additional burstprotection structures installed directly round about the housing. Oneaspect of the present invention is being able to do without elaborateburst protection design and/or solid flow-conducting housing structures.

Furthermore, there is the problem with exhaust gas turbochargers knownfrom the prior art that components that are coupled to one anotherexpand in their elongation behaviour significantly differently. In thecase of conventional connections between such components, high screwstresses occur for example through elongation blockages andcorresponding wear through relative movements in the contact surfaces.It is likewise desirable to realise an optimisation of thesedisadvantageous characteristics of elongation behaviour with the idea ofone aspect of the present invention.

SUMMARY OF THE INVENTION

One Aspect of the invention is therefore based on overcoming theaforementioned disadvantages and propose an improved solution for anexhaust gas turbocharger, which has a safe operating behaviour with ahigh efficiency and in particular possesses an improvement regarding theproblems of the transient elongation.

One aspect of the present invention is being able to do withoutelaborate burst protection design and/or solid flow-conducting housingstructures. It is likewise desirable to realise an optimisation of thesedisadvantageous characteristics of elongation behaviour with the idea ofone aspect of the present invention.

A basic idea of one aspect of the present invention is that thecharacteristics of materials with negative Poisson's ratio (transversalcontraction number) in certain regions of the housing or of theturbocharger are used in order to specifically influence the elongationbehaviour of affected regions.

According to one aspect of the invention, a new type of use of anauxetic material or of an auxetic structure with a negative Poisson'sratio is accordingly proposed in or on an exhaust gas turbocharger on aor between two adjacent components for influencing thermal and transientelongations.

In an advantageous configuration of the invention, a use of an auxeticmaterial is proposed, wherein the auxetic material or the auxeticstructure is arranged between two housing walls of a turbochargerhousing, in hollow spaces of components of the exhaust gas turbochargerand/or between at least two components of the exhaust gas turbochargeradjoining one another, wherein in the last-mentioned case the auxeticmaterial is preferentially provided as an elastic connecting element.

A further aspect of the present invention relates to an exhaust gasturbocharger with a shaft and at least a compressor wheel arranged onthe shaft and a turbine wheel as well as a housing in which the shaft,the compressor wheel and the turbine wheel are arranged, wherein atleast a part of the housing consists of an auxetic material with anegative Poisson's ratio.

In a preferred configuration of one aspect of the invention the housingcomprises an inner housing wall and an outer housing wall and anintermediate space and the auxetic material (M) is arranged between thehousing walls preferentially entirely in the intermediate space.

By integrating the auxetic structure in the compressor and/orturbine-side housing of a radial or axial exhaust gas turbocharger, theelongation behaviour of the housing can be adapted to the elongationbehaviour of the rotor. The adaptation is effected through the targetedadjustment of the geometric parameters of the auxetic structure. Theadjustment of the geometric parameters is effected in such a manner thattaking into account transient thermal elongations and elongationproportions as a consequence of pressure and centrifugal force theelongation characteristic of the housing is adapted to the elongationcharacteristic of the rotor. By way of this, the radial gap thatmaterialises during the steady-state operation is narrower compared withconvention designs. As a result, a higher efficiency with turbines and agreater surge limit interval can be achieved with compressors.

It is advantageous, furthermore, when the auxetic material is entirelyarranged in the region round about the compressor wheel and/or theturbine wheel, preferentially between the housing walls, as a result ofwhich an additional safety effect for the event of a bursting of theturbocharger is established. Here, the auxetic structure is integratedin the housing structure as crash zone for absorbing kinetic energyduring the impact of a rotating component and consequently increases thesafety against components and/or component fragments exiting without anoteworthy increase in weight.

It is advantageous, furthermore, when between at least two adjoiningcomponents of the exhaust gas turbocharger an elastic connecting elementis arranged, which consists of an auxetic material with a negativePoisson's ratio (for example between the bearing housing and the turbineinflow housing). The structure can be for example printed on or appliedto a component or both components or be attached to the two componentswith connecting elements that are not described in more detail.

Alternatively, the two adjacent components can be directly connected toone another by way of the auxetic material.

In a further advantageous embodiment of the invention it is providedthat hollow spaces are provided in the housing which are filled with theauxetic material. By suitably configuring the structure, the requiredstiffness is adjusted so that despite the low weight the requirements interms of vibration are fulfilled.

It is likewise advantageous when auxetic material is coated on orapplied to components of the exhaust gas turbocharger whose elongationis to be influenced.

The inventive concept can be used in particular with the followingexhaust gas turbochargers: radial turbochargers, axial turbochargers,turbo blowers, or turbines (power turbine).

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantageous further developments of the invention are marked inthe subclaims or are shown by way of the figures in the followingtogether with the description of the preferred embodiment of theinvention. It shows:

FIG. 1 is a first schematic exemplary embodiment of the presentinvention; and

FIG. 2 is an alternative schematic exemplary embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

In the following, the invention is explained in more detail makingreference to the FIGS. 1 and 2, wherein same reference characters in thefigures point to same structural and/or functional features.

In FIG. 1, a first purely schematic exemplary embodiment of the presentinvention is shown. Shown is an extract of a housing 3 of an exhaust gasturbocharger with a rotor L (e.g. a turbine wheel T or a compressorwheel V) with rotor blades 7. The rotor L is arranged on a shaft 2 inthe housing 3.

The housing 3 has an inner housing wall 4 and an outer housing wall 5,wherein an auxetic material M or an auxetic structure with a negativePoisson's ratio is arranged between the two housing walls 4, 5.

Between the rotor blades 7 and the inner housing wall 4 a gap S isprovided as intended.

In the shown exemplary embodiment, the auxetic material M is entirelyarranged in the region round about the rotor L between the housing walls4, 5.

FIG. 2 shows an alternative schematic exemplary embodiment of thepresent invention. Shown are a component B1 and a component B2 of anexhaust gas turbocharger, wherein between the two adjacent, i.e.adjoining components B1, B2 of the exhaust gas turbocharger an elasticconnecting element 10 is arranged, which consists of an auxetic materialM or of an auxetic structure M with a negative Poisson's ratio. There,the two adjacent components B1, B2 are directly connected to one anotherby the auxetic material M.

In its embodiment, the invention is not restricted to the preferredexemplary embodiments stated above. On the contrary, a number ofversions is conceivable which also makes use of the presented solutioneven with embodiments of fundamentally different type.

Thus, while there have shown and described and pointed out fundamentalnovel features of the invention as applied to a preferred embodimentthereof, it will be understood that various omissions and substitutionsand changes in the form and details of the devices illustrated, and intheir operation, may be made by those skilled in the art withoutdeparting from the spirit of the invention. For example, it is expresslyintended that all combinations of those elements and/or method stepswhich perform substantially the same function in substantially the sameway to achieve the same results are within the scope of the invention.Moreover, it should be recognized that structures and/or elements and/ormethod steps shown and/or described in connection with any disclosedform or embodiment of the invention may be incorporated in any otherdisclosed or described or suggested form or embodiment as a generalmatter of design choice. It is the intention, therefore, to be limitedonly as indicated by the scope of the claims appended hereto.

1. An exhaust gas turbocharger comprising: at least two adjacentcomponents; and one of an auxetic material or of an auxetic structurewith a negative Poisson's ratio in or on the exhaust gas turbochargerbetween the at least two adjacent components configured to influencethermal and transient elongations.
 2. The exhaust gas turbocharger ofclaim 1, wherein the auxetic material or the auxetic structure comprisesan elastic connecting element arranged between the at least two adjacentcomponents configured as two housing walls, in hollow spaces ofcomponents of the exhaust gas turbocharger or between the at least twoadjacent components of the exhaust gas turbocharger adjoining oneanother.
 3. An exhaust gas turbocharger comprising: a shaft; at leastone compressor wheel arranged on the shaft; a turbine wheel; and ahousing in which the shaft, the at least one compressor wheel, and theturbine wheel are arranged, wherein at least a part of the housing hasan auxetic material with a negative Poisson's ratio.
 4. The exhaust gasturbocharger according to claim 3, wherein the housing comprises: aninner housing wall; and an outer housing wall; wherein the auxeticmaterial is arranged between the inner housing wall and the outerhousing wall.
 5. The exhaust gas turbocharger according to claim 3,wherein the auxetic material is entirely arranged in a regionsurrounding at least one of the at least one compressor wheel and theturbine wheel.
 6. The exhaust gas turbocharger according to claim 3,further comprising: an elastic connecting element arranged between atleast two adjoining components of the exhaust gas turbocharger, theelastic connecting element comprises the auxetic material.
 7. Theexhaust gas turbocharger according to claim 6, wherein the at least twoadjoining components are directly connected to one another by theauxetic material.
 8. The exhaust gas turbocharger according to claim 3,wherein cavities are provided in the housing that are filled with theauxetic material.
 9. The exhaust gas turbocharger according to claim 3,wherein the auxetic material is one of coated on or applied tocomponents of the exhaust gas turbocharger.
 10. The exhaust gasturbocharger according to claim 3, wherein the exhaust gas turbochargeris a radial turbocharger, an axial turbocharger, a turboblower, or aturbine.
 11. The exhaust gas turbocharger according to claim 4, whereinthe auxetic material is entirely arranged in a region surrounding atleast one of the at least one compressor wheel and the turbine wheelbetween the inner housing wall and the outer housing wall.